misc fixes: remove forceConst (obsolete by static), add more runnableExamples to system (#17896)

* misc fixes

* add runnableExamples for compileOption

* add runnableExamples for runnableExamples

* move tconsteval => tconst

* cleanup

tests/vm/tconst.nim

@@ -0,0 +1,35 @@
+discard """
+  targets: "c cpp js"
+"""
+
+import std/strutils
+
+template forceConst(a: untyped): untyped =
+  ## Force evaluation at CT, but `static(a)` is simpler
+  const ret = a
+  ret
+
+proc isNimVm(): bool =
+  when nimvm: result = true
+  else: result = false
+
+block:
+  doAssert forceConst(isNimVm())
+  doAssert not isNimVm()
+  doAssert forceConst(isNimVm()) == static(isNimVm())
+  doAssert forceConst(isNimVm()) == isNimVm().static
+
+template main() =
+  # xxx merge more const related tests here
+  block:
+    const
+      a = """
+    Version $1|
+    Compiled at: $2, $3
+    """ % [NimVersion & spaces(44-len(NimVersion)), CompileDate, CompileTime]
+    let b = $a
+    doAssert CompileTime in b
+    doAssert NimVersion in b
+
+static: main()
+main()